Method of forming cores for dynamo-electric machines



July 25, 1933. T. A. WRY

METHOD OF FORMING CORES FOR DYNAMO ELECTRIC MACHINES Filed 001 26, 1932Ihvehtor: Thomasi A. WF

Wad/4k His Attorney.

Patented July 25, 1933- UNITED STATES PATENT OFFICE THOMAS A. WRY, OELYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATIONOF NEW YORK METHOD OF FORMING CORES FOR DYNAMO-ELECTRIC MACHINESApplication filed October 26, 1932. Serial No. 639,626.

In the construction of dynamo electric machines, a large item of expenseis the magnetic steel used in the construction of the stator and rotorcores. This is particularly true where silicon steel is used for thepurpose. The established practice is topunch rings or round disks fromsheet stock for the smaller size machine and to punch segments for thelarger sizes. In both cases,

each punching is provided with teeth between which are slots to receivethe windings. In many cases, the punchings are also provided withexternal perforated lugs to receive clamping bolts. Punching round orsegmental objects Zfrom rectangular sheet stock results in a largeamount of scrap which substantially increases the cost of manufacture.Furthermore, commercial sheet steel as obtained from the manufacturersis not of exactly the same thickness throughout the sheet. 'Due to this,it is the custom in assembling a core structure to pile a certain numberof disks or pieces forming a set in place, then to pile a second set ontop of the first but angularly advanced with respect thereto by acertain amount, then add more disks or pieces angularly advanced fromthe second and so on, the purpose being to average the inequalities inthe total assemblage and avoid small spaces between adjacentlaminations. Such a method of procedure increases thecost of assembly,and also results in a structure in which the grain of the steel insteadof extending uniformly in one direction throughout the core, as itshould to attain the best electrical results, extends in a number ofdifferent directions, depending principally upon the number oflaminations in each of the aforesaid sets.

My invention has for its object an improved method of making coreswhereby the cost of laminated stator and rotor cores is decreased byutilizing the stock in a more economical maner and at the same timeproviding a core in which the grain of the steel extends uniformly inthe same direction.

For a consideration of what I believe to be novel and my invention,attention is directed to the accompanying description and the claimsappended thereto.

In the accompanying drawing, which is illustrative of my invention, Fig.1 is a plan view of a piece of strip stock having teeth and coil slotsout along one edge; Fig. 2 illustrates my,impr0ved method of cutting twopieces of core stock from a single strip of steel with interlockingteeth and coil slots; Fig. 3 shows one of said strips partially bent inan edgewise manner, and Fig. i shows a complete stator core, 1 4

In Fig. 1 is shown a piecepf strip stock having teeth 5v and coil slots6, said teeth being parallel to each other and having overhanging ends 7which serve in part to confine the windings within the coil slots in thefinal assembly. In such a construction, all of the stock removed frombetween the teeth to form the coil slots is scrap material. Thearrangement is more economical of material than where disks and segmentsare cut from large sheets of stock.

No claim is made herein to the method of cutting teeth and slots alongone edge of a strip of magnetic material as indicated in Fig. 1, andsubsequently winding said strip edgewise to form a core as it is theinvention of Louis E. Underwood and forms the subject matter of his aplication for patent Serial No. 639,622 filed ctober 26, 1932.

I have discovered thatfurther and substantial savings may be effected bychoosing proper tooth and coil slot dimensions. or sizes and utilizingwhat is waste material in the type shown as Fig. 1 to form teeth inanother or companion strip. The strip stock shown in Fig.2 is only 43%wider than the stock shown in Fig. 1 yet by this increase, I am able toform two toothed strips, and with ract'ically no waste. From Fig. 2, itwill e seen that the outer end 8 of each tooth is aligned with thebottom of the coil slot in the companion strip, and that only a singlecutting of the stock at this point is required to severthe parts. Theonly waste in this construction is the very small pieces 9 locatedbetween the sides of each tooth on one strip and the side walls of theteeth forming the coil slots of the companion strip. By suitable dies,the stock is divided .into two strips and the teeth and coil slotsformed 100 ruts, one on eachside of the waste stock9. Also that .each ofsaid parallel cuts extends to the bottom of the coil slot at one end andterminates just short of the bottom of a slot at the other end anddefines the overhanging" portion of the tooth. The size and shape of theteeth and slots maybe varied from.

that shown to suit the electrical characteristics of the machine useingthe core but the method of cutting the stock will be the same. As thedivided stock passes through a suit able punch press containing'thedies,.it is necessary to sep'arate the str ps by raisingor lowering onestrip with respect to the other to free the teeth of one set from thoseof the other. f

After the strip is so formed with its teeth and coil slots, it is woundedgewise to form a helix of fine pitch. 1 In other words, to form afinished core in which all of the teeth and slots of the numerous turnsare in exact axial register. In Fig. 3 is shown a straight strip, oneend of which is bent edgewise and also illustrating how the teethwliiclrwere initially parallel are moved to radial'positions. withrespect to a common center, the latter being the axis of the shaftcarrying the rotor of the completed machine.

In Fig. ;4 is shown a helically wound core ready for assembly in asuitable frame. The core may be secured or clamped in the frame in anywell known manner. V

The invention is illustrated in connection with a stator in which thecoil slots open v toward the center or bore but it is also" applicableto the formation of rotorsyhaving peripheral windings bymerelybending-the strip edgewise in the opposite direction with the teethprojecting outwardly.

Bending steel stock edgewise and at the same time confining eachturn toa substantially uniform cross section; from the inner to the outer edge,as must be doneto obtain the best results, causes strains in the stockand for that reason I anneal the core after being formedand prior tobeing put into use. For this purpose, any suitable'annealfj ingfurnacemay be used.

A machine suitable for windingv steel edgewise is described and claimedin the applicaing the helices.

viously set forth, a strip of stock to form two toothed strips need onlybe 43% wider requirements for a given production are of the order of 10tons, they may be reduced to the order of 3 tons by the use of myinvention. For stock, I may use steel sheets and cut them into stripsand unite the short strips at their ends by welding or other means toform a long strip, or stock in the form of long strips or ribbons madeby steel manufacturers maybe used and weldedwhen necessary to utilizethe short ends left after the formation of one or more helices.

What I claim as new and desire to secure by Letters'Patent of the UnitedStates is: 1. The method of making toothed cores for electrical machineswhich comprises cutting a long narrow piece of magnetic materiallongitudinally into two narrow strips allel teeth and slots with theteeth in one strip occupying the slots between teeth on thanasinglestrip cut in the manner shown in Fig; l. Stated another way, ifthe steel the other strip, separating the strips, and

finally bending each of the" strips edgewise to form ahelix with theslots in axial register. l i

2; The method of'making cores for electrical machines having overhangingteeth and coil slots betweenteeth which comprises taking a single stripof stock, making short cuts in two parallel longitudinal planes, each ofsaid cuts forming the outer end of a tooth and the bottom of a coilslot, cutting the strip in planes perpendicular to the first mentionedcuts to form the sides of the v teeth,separating' the strips so .formedand and the bottom of a coil slot, cutting the strip in parallel planesperpendicular to the first mentioned cuts to form thesides of theteeth,'removing the stock between said parallel cuts, bending each stripedgewise to form a fine pitch helix, and finally anneal- THOMAS A. WRY.

